Factors predicting mortality in invasive pneumococcal disease in adults in Alberta

To define the factors associated with 30-day mortality among adult patients with invasive pneumococcal disease (IPD), we conducted a retrospective review of all cases of IPD in Alberta from 2000 to 2004. We hypothesized that multiple factors would be predictive of such mortality. We also examined the factors predictive of early (within 5 days of admission) mortality. We identified 1154 patients who met our inclusion criteria, 163 (14.1%) of whom died within 30 days. Over half (62.6%) of the deaths occurred within 5 days of admission. Ten factors were independently associated with increased 30-day mortality: 3 comorbidity factors-cancer within 5 years of diagnosis of IPD, diabetes, and cirrhosis; 4 complications-requirement for supplemental oxygen, mechanical ventilation, alteration of mental status, and cardiac arrest; 2 microorganism-related factors-infection with high- or infection with intermediate-mortality serotypes; and 1 treatment-related factor-treatment with a single antibiotic. Age 18-40 years and treatment with 2 antibiotics concurrently were associated with lower 30-day mortality. Comorbid illnesses were not contributory to early mortality (within 5 days of admission); instead, complications (alteration of mental status, requirement for supplemental oxygen, mechanical ventilation, and cardiac arrest) as well as infection with high-mortality serotypes and treatment with a single antibiotic were important. Age 18-40 years, infection with serotypes in the polysaccharide vaccine, and treatment with 2 or more than 2 antibiotics were associated with decreased early mortality. Early mortality accounted for 62.6% of the deaths. In conclusion, we found that mortality in IPD is multifactorial, the factors differ for 5- and 30-day mortality, and mortality is associated with host (age and complications), microorganism (pneumococcal serotypes), and therapeutic factors. Our data indicate that treatment with 2 or more antibiotics effective against Streptococcus pneumoniae should be used to treat IPD.